A conventional switchgear enclosure for housing a circuit breaker has a door with a front-arranged gasket, such as that disclosed U.S. Pat. No. 8,960,815 B2, the content of which is hereby incorporated by reference into this specification. FIG. 1 shows an example of such a gasket 10 mounted to a door 12 of a switchgear enclosure so that when the door is closed, the gasket surrounds a periphery of an opening in the enclosure case so as to seal the case. As shown in FIG. 2, a door bracket 14 is mounted to the door 12 and the gasket 10 is mounted to the bracket 14. A compressible seal portion 16 of the gasket 10 is adjacent to an outer, front face 18 of the enclosure case 20 of a switchgear enclosure, generally indicated at 27. The front face 18 surrounds the opening (not shown) in the case 20. Thus, when the door is closed, the seal portion 16 is compressed against the front face 18 to seal the case 20. It is noted that the seal portion 16 is shown in an uncompressed state in FIG. 2, to show the gasket shape. The conventional gasket 10 is considered to be a front-sealing arrangement since seal portion 16 engages the front face 18 of the case 20, generally along an axis A that extends through the door 12 and the case 20.
The conventional front-sealing gasket 10 of FIGS. 1 and 2 can be affected by the deformation of the case 20 when the case and gasket are subjected to pressure caused by an internal arc. Thus, the gasket 10 can fail to seal the case 20 under such pressure. In addition, currently it is necessary to build a specific case 20 and increase its rigidity for every increase step of rating circuit breaker parameters (e.g., from 31.5 kA to 40 kA to 50 kA to 63 kA).
There is a need for a door suitable for various rated enclosures of switchgear that can withstand pressures caused by an internal arc and also a need for a gasket, between the door and the enclosure case, which remains sealed even when the enclosure door is moved by the pressure wave generated by the internal arc.